1Fast400 said:
Mine was 8.6 when done. How do we know his motor is 8:1? Just because the pistons are, means nothing. Figuring CR accurately is a pretty involved formula, you'd need to cc the head.
Good question 1Fast. As Silver said, the formula is rather easy. pi R squared x cylinder depth at BDC as a ratio to the same at TDC.
JM lists a substantial range of chamber size (58-82cc), so I would have to ask what the standard Striker Street head volume measures. The 8:1 size I quoted is for what I believe is the net CR for an otherwise unmodified engine. I believe my cylinders were honed to 10 over, adding to the cylinder volume, thus raising the net CR. So, we could certainly guesstimate based on the difference in chamber volumes plus the .010 over to get close. My builder said that my net CR ought to be in the 8.2:1 range (he has built several engines with the various JM heads too). That's close enough for me.
But in any case, I obviously lowered the CR for supercharging. The X-Metal upgraded system is unpacked and ready to install.
As far as intake stuff is concerned, head-intake port matching is all that I had done. I personally believe that the GenIII intake has some serious shortcomings, especially after talking with Sean Roe about how lean that intake goes on certain cylinders when under boost (over a full point on the AFR!), and you can guess which ones I'm talking about!
Spending a dime on making that manifold flow better (aside from port matching) would be a dime wasted, IMHO. I almost went with a GENII intake, but didn't want the extra workto adapt it. Besides, I already had Boomer coat my stocker. It may be a project for another day though...
I did go with an RSI single-blade throttle body (someone asked about larger throttle bodies), that should help a bit to reduce bottle-necking there.
The numbers listed were from an engine dyno, and the truck put down a best of 438rwtq on the chassis dyno before I broke it (only mods at the time were a K&N CAI and Mag cat back).
For those of you who don't know, I broke #3 with an STS turbo system on it. For those of you who did know, I sold that kit to someone who made it work with a different engine management system. The sytem was putting out 12psi, WAY more than the 6psi it was supposed to!!
Between the overboost, and the fact that the STS fuel system didn't have a program loaded into it made quick work of that piston.
The engine is in transit, and scheduled to arrive on the 28th. With a bit of luck, and some hard work, I ought to have the engine in and running by March's Seattle/Tacoma GTG. A few weeks after that, we ought to be getting those custom diff/axle assemblies in, and I'll put the Caltracks on at the same time. This rig with 4.56 gears and slicks should be a helluva ride.
I hope to get some time to run plenty of passes at our local strip before the MoPar drags at SIR this summer. I'm a complete newbie when it comes to drag racing, so it's time to get experienced.
